In the processing of materials such as ceramics, thermal uniformity is often required to achieve uniform heating of the product and to minimize opportunities for distortion, bending or cracking of the product by reason of uneven heating. A system is shown in U.S. Patent Publication No. U.S. 2004-0173608 A1 (U.S. patent application Ser. No. 10/775,542), assigned to the same assignee as the present application, wherein uniform heating is provided by one or more eductors in the furnace chamber which produce high volume gas circulation in the furnace to achieve a highly uniform gas environment and temperature. The one or more eductors can also be employed for forced convection cooling of a product. The one or more eductors are preferably as shown in U.S. Pat. No. 5,795,146, which is also assigned to the assignee of the present invention. The eductors provide high volume flow necessary for improved temperature uniformity and control and can provide a thermal uniformity of about ±3.5° C. during the process cycle.